[leetcode] Maximal Square

int maximalSquare(vector<vector<char>>& matrix) {
int result = 0;
if(matrix.empty())
return result;
const int n = matrix.size();
const int m = matrix[0].size();
vector<vector<int> > dp(n + 1, vector<int>(m + 1, 0));
for(int i = 0; i < n; ++i)
for(int j = 0; j < m; ++j){
if(matrix[i][j] == '1'){
dp[i + 1][j + 1] = min(dp[i][j], min(dp[i + 1][j], dp[i][j + 1])) + 1;
result = max(result, dp[i + 1][j + 1]);
}
}
return result * result;
}